Line fuse



Aug. 10, 1954 J. c. RosE 2,686,240-

LINE FUSE Filed July 2l, 1950 55 .3/ gf 9 v 23 2 04, sa 5g 75@ f@ *T6222'/ TTO/P/VEV.

Patented Aug. 10, 1954 LINE FUSE J ess C. Rose, North Holl J. G.McAlister, Inc.

poration of California Application July 21, 1950, Serial No. 175,062 8Claims. (Cl. 20D-415.5)

This invention relates to a fused conductor connector, and moreparticularly to a connector between the free ends of two iiexibleconductor cables, which is both a connector and a loadlimiting circuitinterrupter.

While the'principles of'the'invention have application iny a Wide field'of electrical circuitsl of many different types it has particularapplication to conditions such` as obtain in moving picture andtelevision studios; In these studies portable lights drawing currents ofheavy amperageare used'. Insulatedflexible conductor cables lead fromeach lighting device to any, one of a number. of` conveniently locatedbuss bars or other current distributors, each distributor supplyingcurrentf'or anumber ofsuch lamps.

When, as `is usually the case, the source of` supply is froma centertapped'single phase, 220'volt, transformer secondary, or a 110-220 voltAthree wire direct current source, the three power line wires are.connected to a three terminal distributor, to the outside. legs of whichthe-one wire of several of the two wire lamp cables vare connected inapproximate balance, the returny wires of. the cables from allthevlampsbeing connected to the grounded middle leg. of4 they distributor. Theseconnections for thesake of,` rapidity of operation are made at. the endsof` each ofx the wires of the cables byv terminal. clamps. The threefeed wires to the distributor areY provided with circuit interrupters,either fuses or circuit breakers, of a size to protect the feeder linesfrom the load of allthe lamp connections supplied bythe distributor, butthe protection oftheindividual lamps and individual lamp circuits fromvoverloads caused by a1 short circuit in thelamp or between the two cablewires or otherwise, has presented a problem, of which thisinvention-provides a solution.

The problemi is made difficultv bythe conditions-in the studios. Thelamp cables from the buss bar. or other distributor lie on the iioor orare strung around the studio in frequently changed locations, usually:in exposed positions wherer they are subject to trampling by vehiclesand4 to other hardusage. If each lamp cable is ya single two wire linewithout distributing connections to other lamps between the distributorand the one lamp, a separate cablel is provided fbr each lamp; Forproper overload protection of both the lamp and cable, the/expensiveprovision of a' numbery of individual fused outlets at each distributorbecomes necessary in lieu of the customary rapidly operated' andconvenient clamps;

ywood, Calif., assignor to Los Angeles, Calif., a cor- Since two singlewire connections are made at the distributor for each lamp, it followsthat if the system of terminal clamps is to be used, the logical placeto fuse a lamp and lamp circuit is in the ho-t wire of the cable betweenthe point at which it emerges from the cable and the terminal clampwhich secures that wire to the buss bar terminal. The entire lampcircuit is then positively assured of overload protection.

This invention provides such a single wire combination connector andfuse for use close to the buss bar terminal. It is an object of theinvention to provide a fused connector for a single flexible conductor,which shall be compact, readily operated, inexpensive of manufacture,capable of withstanding hardusage, and of simple construction.

It isanother object to provide such a connector, which shall be quicklyand inexpensively re-fused.

It is another object to provide such a connector constructed for readyassembly and disassembly with two slidably joined parts, the conductorsof the connector being incapable of making a conducting contact untilthe two parts are joined together to provide a completely enclosedchamber for the fuse.V This prevents the fuse from blowing, by reason ofa pre-existing short circuit, as the two partsare being broughttogether, before they have moved toward each other sufficiently toenclose the fuse, eliminating any fire hazard or injury to persons fromnames blown outside the casing;

It is also an object of the invention toV provide a fused connectorwhich will completely enclose the fuse in a substantially gas tightchamber, but provide forvslow escape of the gases, generated by theblowing of the fuse, over a baiiied course so as to prevent the jettingof llame into the ambient.

The invention is herein disclosed as embodied in a fused connector foruse with illuminating equipment of moving picture and televisionstudios, but the principles of the invention are applicable whereveroverload protection is desired. Under different conditions, suchprotection may be conveniently associated with a line connector havingutility other than as a mounting for the fuss` element. Or a fusedconnector embodying the principles of the invention may be usedvtoprotect both sides of the circuit, providing two connections and twofuses in the same casing. The invention, therefore, is not limited totheparticular embodiment shown in the-drawings andA set forth in thefollowing description, but embraces any device which comes within thespirit of the invention as defined in the appended claims.

In the drawings:

Figure l is a schematic View of a circuit embodying the invention. lnthis view the connector is shown in top plan view.

Figure 2 is an exploded View of the connector, showing the two parts ofthe casing pulled apart for examination or replacement of the fuseelement.

Figure 3 is a vertical sectional view of the connector showing someparts in side elevation.

Figure 4 is a fragmentary top plan view of one end of the connector withthe adjacent part of the casing horizontally sectioned to show theterminal structure within the casing.

Figure 5 is a fragmentary sectional View showing an alternative form ofspacer ring.

Figure 6 is a sectional view taken along the line 6 6 of Figure 3.

In Figure l there is shown schematically a simple circuit in which thefused connector of this invention is used. A conductor l l is connectedto one of the terminals at one end of the buss bar l2 and to theconnector i3 at its other end. Conductor lil leads from the connector E3to a lamp indicated diagrammatically at i5 and is sheathed in the cableIS with a return conductor lli which connectsthe lamp i5 with the centerterminal of the buss bar, completing a standard l le volt lamp circuit.The ends of conductors i i and It are usually equipped with terminalclamps by which they may be rapidly connected or disconnected to thebuss bar terminals. Conductors ill and IE5 at the lamp end of the cableitl are plugged into a suitable terminal receptor on the lamp structure.

The fused connector le comprises a two part casing Il made of insulatingmaterial and two terminal structures i8 and i9, the structure i8 beingrigidly mounted and secured in the left- Yward casing part 2t, and thestructure i9 being rigidly mounted and secured in the rightward casingpart 2 l The casing is in the general form of a hollow closed endcylinder, providing a cylindrical interior chamber in which the terminalstructures, including the fuse element 22, are mechanically protected,are insulated electrically from surrounding objects outside the casing,and by which the fuse is prevented when it blows from setting re toiniiammable objects or injuring the studio personnel. The left end ofthe casing shell has secured to it by the retaining screws 23 aninsulating end closure plug 25 which has a central aperture 25 for thereception of the insulated conductor ld. The right end of the casingshell similarly has secured to it by retaining screws 2B an insulatingend closure plug 2l which has a central aperture 28 for the reception ofthe insulated conductor I i. The inner end of each closure plug is ofreduced diameter to provide an annular recess over which the cylindricalshell of the casing fits, giving the casing a smoothly contouredcylindrical exterior surface. The closure plugs are rounded at theirouter ends, this feature and the smooth exterior surface of the shellenabling the connector to be dragged over the studio iioor and othersurfaces without danger of being caught and torn loose from theconductors.

The rightward part 3Q of the shell has a telescopically slidingconnecting joint at 3l with the rightward part 32. The outsidediametersof the parts are the same. The rightward part 32 has aninwardly projecting skirt 33, providing a shoulder 3', against which therightward end part of the shell abuts when the two parts are pushed intohome position. rIhe retaining screw 35 holds them immovably in thisposition.

The leftward terminal structure i8 is permanently and rigidly mounted onthe leftward part 2!) of the casing and when the two casing parts arepulled apart at the joint 3l, this terminal structure stays intact inleftward casing part 20. This terminal structure comprises a socketmember 3e of brass or other conducting material which is formed with acentral recess 3l on its left end into which the wire core of theconductor Il! is soldered, and with a ngered socket 38 on its right endfor the reception of the contact pin 39 of the rightward terminalstructure. The leftward terminal structure is completed by the ringfill, preferably of insulating material, which is fastened to the socketmember 3e by the screw i I, this ring being in turn secured to thecasing shell part 3Q.

The rightward terminal structure l@ comprises the contact pin member 42,the conductor connecting member d3, both of brass or the like, and aconnecting bridge or dielectric frame member fill of insulatingmaterial, which is rigidly secured by the two bolts 5 to the two lugs 45respectively on the juxtaposed ends of the pin member [i2 and cableconnecting member lit. The fuse element lll is also secured or mountedby means of these bolts to the lugs 4i6 but on the side of the lugsopposite the bridge liti. The lugs are preferably threaded to receivethe threaded Shanks of the bolts. Since each nut is disposed at the fuseend of its bolt and the bolts are held in position by reason of theirthreaded relation to the lugs, this mounting means permits the nuts tobe removed and the fuse replaced without disassembling the pin member52, the bridge or frame ifi and the conductor connecting member 63,simplifying and shortening the ire-fusing operatio'n.

The contact pin member i2 carries the contact pin 39 sized to snuglymate with the fingered socket 38. The socket iingers are rounded attheir outer ends to facilitate the entry of the pin 39. The Contact pinmember d2 is centered in the leftward shell part 20 by an insulatingring i9 secured to the pin member by a set screw 5d. This ring slidesalong the bore surface of the shell part 2t and is of a diameter to giveit a slight clearance with respect to this bore surface for two reasons.The gases formed when the fuse blows may escape through this clearanceto the chamber to the left of the ring, from which chamber the gases mayslowly bleed through very small bleeder holes 52 in the casing shellaround this chamber. The second advantage will appear from aconsideration of the manner in which terminal structure I9 is mounted inthe rightward shell part 2 i.

The conductor connecting member 43 is soldered to the wire core of theconductor ll in the same manner as has been described above forconductor hi. The member d3 has fastened to it an insulating ring 53 bythe set screw 54, which in turn is secured to the rightward casing shellportion by the retaining screw 55. lt is then clear that the casing part2| and the entire rightward terminal structure E@ from the contact pin39 to the conductor l l, including the rings e9 and 53, the fuse Lil,bridge .te and conductor ll move bodily as a single substantially rigidsub-assembly, when the retaining screw 35 is removed and the two partsof the casing are pulled apart. Similarly the leftward terminalstructure moves with itsrseveral associated parts asa single subassemblywith the leftward casing partZQ.

These two subassemblies are related to each other in the same fashion asare the two parts of an ordinary plug and socket connector, and theaddition of the fuse to one subassembly does not destroy the similarity.rhe use and fuse holder are secured to, and are removable with, the oneend of the connector, a feature of construction which simplies thehandling of the device when a fuse is to be replaced.

For easier fabrication and greater strength the retaining screw is of alength to be threaded into the ring 53. When the two parts of theconnector are moved toward each other for inal assembly, the pin 3S andring le are first to enter the shell of the leftward' part of theconnector. The slight clearance between the ring 119 and the leftwardshell facilitates the entry movement. Since the length 54 of thetelescopic joint between the shell parts is greater than the distance 55between the extreme left end of the contact pin 39 and the extreme rightend of the fingered socket 38, the chamber surrounding the fuse betweenrings i9 and 53 will be formed and Iclosed prior to the making ofcontact between the ccntact pin and ngered socket. Ii, then, there is anundiscovered short which has not been corrected at the time the casingparts are being slid into their home position, the fuse will olow, butthis will not happen until the fuse chamber has been formed, andthedanger of ire to surrounding objects' and injury to the operator arethereby eliminated.

Figure 5 shows a modification of the contact pin member. Instead of thesingle insulating ring 49 of Figure 3, a triple finned brass ring 55 isformed integrally with the remainder of the contact pin member. The rimsurfaces of this triple ring 55 have a substantially close sliding t'with the bore surface of the casing. Small drilled bleeder holes 5l arethen provided transversely through the rings, the holes in one ringbeing in staggered relation to the holes in the other rings, The ringsthen act like ba'le plates to break up jets of flame from a blown fuse,while yet permitting the passage of the gases from the disintegratedfuse through the rings to relieve the gas pressure in the inner fusechamber.

The foregoing description of the fused connector reveals its uses, themanner in which it is re-fused and the advantages which come from itsincorporation in an electrical circuit in the way described.

I claim:

1. A connector for connecting two insulated electrical conductorscomp-rising: a rst rigidly and permanently assembled terminal fixturemechanically and electrically adapted to be secured to a free end of oneof said conductors; a second rigidly and permanently assembled terminalxture adapted to be mechanically and electrically secured to the freeend or" the other of said conductors; said nxtures each comprising acasing tube or" insulating material having an aperture at its outer end,and a conductor terminal structure permanently and rigidly securedwithin the tube, the casinfy tubes slidaoly telescopically engaging eachother at their inner open ends, and providing a substantially gas tightenvelope of insulating material for the terminal structures, said freeends1 oi the insulated conductors entering the casing tubes through theapertured outer ends thereof respectively for securement to the terminalstructures respectively, the terminal structures having pin and socketelectrical contacts for engagement with each other when the tubes aremoved toward one an.- other into telescoped position, and one of theterminal structures having mounting means interposed in its conductancepath for supporting an overload fuse; interengaging means on the tubesand terminal structures for constraining the fixtures and consequentlythe tubes and terminal structures to move in parallel straight lines,each with respect to the other, while they are being telescopicallyjoined; and means for securely fastening the casing tubes together whentelescopically joined.

2. A connector for use between the ends of two conductors, comprising: atwo-part tubular casing, each part having a closed end, apertured topass one of the conductors, and the two parts having a sliding gas-tighttelescopic joint for holding them in relatively assembled position, afirst terminal structure Xedly mounted and fastened in one casing partand arranged for securement to its associated conductor end, a contactelement on said rst terminal structure, a second terminal structurehaving a rearward position xedly mounted and fastened in the othercasing part, said second terminal structure having a forward portionincluding a contact element for making contact with said contact elementon said nrst terminal structure when the two casing parts are assembledposition, a dielectric frame member included in said second terminalstructure connecting said forward and rearward portions, mounting meanson said forward and rearward portions for connecting a fuse therebetreen, said other casing part having a length sufficient to enclose theentire length of space between said mounting means when the two casingparts are assemble-fl, the two terminal structures being mounted intheir respective casing parts at such positions therealong that when thecasing parts are placed in the initial position of their slidingtelescopic joint the contact of the second terminal structure is out ofelectrical Contact with the contact of the i'lrst terminal structure,and when the two casing parts are in the home position of their jointthe contact element of the second terminal structure is in electricalcontact with the contact or" the first terminal structure.

3. A connector for use between the ends of two conductors, comprising: atwo-part tubular casing, each part having a closed end, apertured topass one of the conductors, and the two parts having a sliding gas-tighttelescopic joint for holding them in relatively hired assembledposition, a nrst terminal structure xedly mounted and fastened in onecasing part and arranged for securement to its associated conductor end,a contact element on said rst terminal structure, a second terminalstructure having a rearward position fixedly mounted and fastened in theother casing part, said second terminal structure having a forwardportion including a contact element for making contact with said contactelement on said nrst terminal structure when the two casing parts are inassembled position, a dielectric frame member included in said secondterminal structure connecting said forward and rearward positions,mounting means at said forward and rearward positions for connecting afuse therebetween, said terminal structures including annular spacersrigidly related to the terminal structures and extending outwardly tothe bore surface of the casing, the nrst terminal structure having aspacer intermediate its connection to its associated conductor end andits place of contact with the second terminal structure, and the secondterminal structure having one spacer adjacent its contact element andthe other spacer adjacent its connection with its associated conductorend, whereby a substantially gas-tight chamber is provided for thecontacting connection between the two terminal structures, and anothersubstantially gas-tight chamber is provided for the space between saidmounting means.

4. The combination dened in claim 3, in which transverse gas bleederholes are formed in the one spacer of the second terminal structure, andgas bleeder holes are provided in the casing between the spacer of therst terminal structure and the one spacer of the second terminalstructure.

5. The combination defined in claim 3, in which the one spacer of thesecond terminal structure has a plurality of proximately adjacent,spaced, parallel ring-like walls, and in which transverse gas bleederholes are formed in each of said walls, the holes in one wall beingstaggered with respect to the holes in an adjoining wall, whereby whenthe fuse blows iiame will not pass through the said parallel walls insingle straight jets.

6. The combination defined in claim 5, in which further gas bleederholes is provided in the casing between the spacer of the first terminalstructure and the one spacer of the second terminal structure.

7. The combination dened in claim 3, in which the casing is of aninsulating material, and the ends thereof are centrally formed with thesaid apertures for passage of the conductor ends, and the said terminalstructures are each provided with a socket at its extreme outer end forsoldering the associated conductor end.

8. The combination defined in claim 3, in which the one casing partextends inwardly a distance suicient to enclose the entire length ofspace between said mounting means when the two parts are in assembledrelationship, and the second part has a telescopic gas-tight joint withthe first part, the terminal structures being mounted in theirrespective casing parts at such positions along said casing parts thatwhen the two casing parts are placed in the initial position of theirtelescopic joint the contact element of the second terminal structure isout of electrical Contact with the first terminal structure, and whenthe two casing parts are in the home position of their joint the contactelement of the second terminal structure is in electrical Contact withthe rst terminal structure, and in which the iirst terminal structureand the contact element of the second terminal structure are formed withpin and socket mating elements, the one spacer of the second terminalstructure is of a diameter to slightly clear the bore surface of thecasing, the other spacer of the second terminal structure engages thebore surface of the second casing part, both casing parts, includingtheir ends are of dielectric material, the apertures for the conductorends are disposed ycentrally of the casing ends, and the said terminalstructures are each formed with sockets at their extreme outer ends forsoldering their associated flexible conductor ends to said terminalstructures.

References Cited in the le of this patent UNITED STATES PATENTS NumberName Date 1,114,366 Knaui Oct. 20, 1914 1,604,373 Wyman Oct. 26, 19261,974,291 Reynolds Sept. 18, 1934 2,046,221 Thomas June 30, 19362,306,340 Lee Dec. 22, 1942 2,375,472 Hollins et al May 8, 1945

